Recovery of N applied as 15N-manure or 15N-gliricidia biomass by maize,cotton and cowpea |
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Authors: | Dário Costa Primo Rômulo Simões Cezar Menezes Everardo Valadares de Sá Barretto Sampaio Marlon da Silva Garrido José Carlos Batista Dubeux Júnior Carla Silva Souza |
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Affiliation: | 1. Universidade Federal de Pernambuco, Av. Prof. Luís Freire, 1000, Cidade Universitária, Recife, PE, CEP 50740-540, Brazil 2. Universidade Federal do Vale do S?o Francisco, Avenida Antonio Carlos Magalh?es, 510, Santo Ant?nio, Juazeiro, BA, CEP: 48902-300, Brazil 3. Universidade Federal Rural de Pernambuco, Av. Dom Manoel de Medeiros, s/n, Dois Irm?os, Recife, PE, CEP 52171-900, Brazil 4. Universidade Federal do Rec?ncavo Baiano, Campus Universitário de Cruz das Almas, Cruz das Almas, BA, CEP 44380-000, Brazil
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Abstract: | Proper management of N applied in fertilizers is important to optimize crop production and to avoid negative environmental impacts. The best way to study N dynamics in the soil plant system is to use fertilizers labeled with 15N. Recoveries of nitrogen following fertilization with 15N-labeled goat (Capra hircus L.) manure and gliricidia (Gliricidia sepium Jacq. Walp) biomass were evaluated in a greenhouse experiment with three successive planting cycles of three crops: maize (Zea mays L.), cotton (Gossypium hirsutum L.), and cowpea (Vigna unguiculata (L.) Walp.). Each 1 kg soil pot received 8 g (equivalent to 20 Mg ha?1) of either manure (12.3 mg g?1 of N) or gliricidia (37.8 mg g?1 of N). Plants were harvested 50 days after germination and real (15N) and apparent recoveries of the applied N were determined. Biomass and N amounts in the cotton and maize crops in all three cycles were higher with gliricidia application than with manure, except for cotton in the first cycle. The biomass of cowpea was also higher with gliricídia in the first and second cycles but the amount of N was significantly higher only in the second cycle. In the first cycle, the largest recoveries of 15N were obtained with gliricidia, for all three crops, but in the second and third cycles recoveries were greater with manure, so that the real recoveries of gliricidia and manure were similar (cotton, 35 and 37 %; maize, 27 and 26 %; and cowpea, 41 and 38 % of the applied N, respectively). Estimates of apparent recoveries were different from the real ones and therefore inadequate for cotton and cowpea. The fast release of N from gliricidia prunings and, on the other hand, the strong residual effect of goat manure-N to subsequent cropping cycles should be considered by farmers in their fertilization strategies. |
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